We are riding a Tacx galaxia roller with a 20" BMX and we thought it would be fun to hook it up with Zwift for some gaming. But it is very slow compair to the roller speed/pedaling. We have tried different tracks and we got some speed down hill but as soon as it gets flat we just spin and everyone drives by. Here is a video with my sons settings. When he starts to ride he goes up to ha 75% of his max speed on the roller. (I also tried to ride and changed the profil to my weight and age but it is still slow) We use Wahoo cadence and speed sensor.
Video link with all the settings and ride: https://imgur.com/a/FIjE7PX